Pressurized-gas vessel and method of making same

ABSTRACT

A pressurized-gas vessel, especially for acetylene and gases soluble in a solvent, which comprises a pressure-retentive metal container, a body of porous material within the container and spaced from a wall thereof to form an intervening space, and a mass of sintered material filling this space and constituting a flame barrier and shock-wave attenuator to prevent explosion of the gas within the vessel while mechanically retaining the mass of porous material against breakdown during handling and transportation of the vessel.

United States Patent Meinass Nov. 20, 1973 [54] PRESSURIZED-GAS VESSEL AND METHOD 3,703,976 11/1972 Hughes et al. 220/88 R K M OF MA ING SA E FOREIGN PATENTS OR APPLICATIONS [75] Invent Helm" Punach, Germany 173,506 4 1922 Great Britain 206/O.7 [73] Assignee: Linde Aktiengesellschaft,

wiesbaden, Germany Primary Examiner-William T. Dixson, Jr.

221 Filed: Mar. 1, 1972 Attorney-(811R ROSS App]. No.2 230,580

Foreign Application Priority Data Mar. 8, 1971 Germany P 21 ll 10 25.8

U.S. Cl. 206/0.7, 220/3, 220/88 R Int. Cl. B6Sd 25/00, Fl7c 11/00 Field of Search 206/0.7; 220/3, 88 B,

References Cited UNITED STATES PATENTS 4/1959 Pater et a1. 206/0.7

[57 ABSTRACT A pressurized-gas vessel, especially for acetylene and gases soluble in a solvent, which comprises a pressureretentive metal container, a body of porous material within the container and spaced from a wall thereof to form an intervening space, and a mass of sintered material filling this space and constituting a flame barrier and shock-wave attenuator to prevent explosion of the gas within the vessel while mechanically retaining the mass of porous material against breakdown during handling and transportation of the vessel.

10 Claims, 2 Drawing Figures PRESSURIZElD-GAS VESSEL AND METHOD OF MAKING SAME FIELD OF THE INVENTION My present invention relates to a pressurized-gas vessel and, more particularly, to a cylinder, flask or bottle for containing and/or dispensing a compressed gas such as acetylene which is soluble in a solvent and is retained, in part, in solution therein. The present invention also relates to an improved method of making such vessels.

BACKGROUND OF THE INVENTION Certain gases, such as acetylene, are transported in and dispensed from metal pressure-retentive vessels containing a mass of a porous material, generally a mineral substance capable of absorbing large volumes of a liquid. The gas is stored in the form of a solution in this liquid, which is, in turn, trapped in the mass within the vessel. The liquid in the case of acetylene is usually acetone.

The vessel is provided with a space free from the porous mass and designed to allow the gas to escape from the solvent and collect in a completely gaseous phase prior to being discharged from the vessel. These systems have several disadvantages, in part resulting from the fact that acetylene and like gases are not only highly combustible, but are also highly explosive, even in the absence of oxygen, when compressed excessively or suddenly. Thus, pressurized-gas vessels of the character described must have a relatively large gascollecting space, generally aove the porous mass, to allow the gas to be introduced into the vessel and to be withdrawn therefrom with rapidity. Furthermore, the presence of a large volume of an explodable gas in the space above and around the porous mass, simply increases the possibility of explosion, both by flashback of an igniting flame or by the rearward transmission of a detonation or shockwave to the vessel from a duct through which the gas is to be dispensed. Such shockwaves may develop when a torch at the downstream side of the conduit is ignited. The presence of a large volume of free acetylene outside the porous solventfilled mass may result in explosion by virtue of a temperature rise within the vessel. Thus, decompositions within the vessel resulting from heating or flashback of an igniting flame, even in the absence of oxygen, will result in a pressure and temperature increase, thereby promoting the possibility of explosion and unduly stressing the vessel.

Another disadvantage of known systems of this character is that, during transportation or handling of the vessel, the porous mass is free to move therein and collides with the metal walls. Such collisions break down the porous mass and reduce the useful life and capacity thereof. The problem is especially pronounced when the vessel is composed of two or more parts connected at a step or like formation against which the porous mass may impact. In this situation, the breakdown of the porous mass increases to the point that a vessel of this construction may be rendered useless after only a brief time.

The porous mass within a conventional pressurizedgas vessel may also be subject to detonation and shockwaves transmitted rearwardly by any duct system which may be connected to the tank. The shockwave, which is applied to the head of the pouous mass, not only stresses the latter to produce additional fissures, cracks or the like (thereby reducing the effectiveness of the mass) but also enables decomposition of the explosive gas deeper within the porous mass.

OBJECTS OF THE INVENTION It is, therefore, an important object of the present invention to provide an improved condenser, tank or ves' sel for a pressurized gas, especially a solvent-soluble explosive gas such as acetylene, whereby the disadvantages of earlier systems can be avoided.

It is another object of the invention to provide a pressurized-gas vessel of the character described which is less sensitive to detonation and shock waves, manifests a lesser tendency toward sustaining decomposition of the gas and explosive reactions, and has a longer useful life than vessels used heretofore for the same purpose.

It is another object of the invention to provide an improved method of making a vessel of the character described.

SUMMARY OF THE INVENTION These objects and others will become apparent hereinafter, are attained in accordance with the present invention, in a system for storing and transporting solvent-soluble explosive gases, wherein the pressureretentive metal vessel receives a porous solventtrapping mass surrounded at least in part by a gascollecting space which is filled or packed with a flame barrier, detonation-wave attenuator and explosionlimiting porous mass of sintered material which simultaneously retains the porous solvent-trapping mass against movement within the vessel and relative to the walls thereof. In other words, an essential feature of the invention resides in filling the intervening space between the porous solvent-trapping mass with a sintered porous body of fine-grained sintered material constituting a flame barrier and a device for attenuating the effect of shockwaves. Heretofore, it has been the practice to determine the capacity of the vessel, reduce the pressure capacity by the maximum pressure increase of a shockwave and determine the operating pressure from this difference. By the use of a flame barrier and attenuator according to the present invention, however, the operating or gas pressure can be markedly raised to the extent to which the effect of the pressure wave is reduced by the attenuator. The pressure and thus the volumetric capacity of the explosive gas can be increased substantially by comparison with conventional systems without rendering the system unable under flashbacks as previously described. Furthermore, the porous mass within the vessel is not able to shift with respect to the walls and thus the system can be handled relatively roughly without damage to this porous mass.

It has been found to be especially advantageous, when acetylene is to be stored, that the body of sintered material have such a grain size as to ensure a pore width which is relatively small in comparison to the pore length. In other words, the pores of the body are relatively narrow and of small cross-section. Under these circumstances, the acetylene can break down or decompose only very slowly with a flame which cannot spread readily because of the long pores when the acetylene pressure lies below a predetennined value. I have found it to be advantageous, with acetylene pressures of 30 atmospheres (absolute) and less to maintain a mean pore width of at most 0.4 mm. Under these conditions, the break-down of acetylene can proceed without detonation. The particles which are sintered together to form the porous sintered mass, preferably are metallic and inert to attack by the solvent or the gas while consisting of spheroids or balls with a diameter of at most 1.6 mm.

According to another feature of the invention, in the regions of the space around the porous body closer to the outlet of the vessel, the sintered mass is thicker and, in the region of the outlet, the porous sintered body has its maximum thickness. The thickness of the sintered body, however, must be kept sufficiently small and the pore cross-section sufficiently large as to permit the pressurized-gas vessel to be filled and emptied in short order. The flame barrier preferably has a melting point which lies below the decomposition temperature of the solubilized gas and solvent. This arrangement has the advantage that, upon decomposition with elevating temperatures, the pores of the sintered flame barrier are blocked and the flow of gas to an explosion region is limited. The melting of the flame barrier also has the effect of withdrawing heat of fusion from the porous body and thereby acts to limit the temperature rise.

Advantageously, the sintered mass is composed of bronze or an aluminum alloy, preferably consisting of 5 to 7 percent by weight silicon, 0.1 to 0.3 percent by weight magnesium, 0.3 to 0.6 percent by weight manganese and 3 to 5 percent by weight copper, the balance being aluminum.

According to another aspect of the invention, the vessel described above is produced by casting the po rous solvent-absorbing mass from an aqueous slurry of the porous material and drying the slurry within the vessel. As a result of the thermal discharge of water from the slurry, the monolithic mass solidifies and shrinks inwardly away from the walls of the vessel to define the intervening space of a cross-section which increases toward the top of the vessel. The intervening space between the porous mass and the metal wall of the vessel is filled with the fine-grained metal particles and the system subjected to a sintering temperature below the transition point of the metal of the vessel and thus below the annealing or embrittlernent temperature of the vessel wall. In the region of the outlet, I prefer to compact the sintered material and to provide additional quantities of the sinterable powder to increase the thickness of the layer.

According to still another feature of the invention, the intervening space is filled with the sinter powder under pressure, i.e., by entrainment with a gas stream which is forced into the vessel under a pressure differential between the interior of the conduit and the interior of the vessel. Preferably, the pressure in the feedline is sufficient to tensionally stress the vessel and thereby place the porous mass, when the pressure is relieved under precompression. As a result, an explosion within the vessel need not place the monolithic porous mass in tension so that breakdown of the solventtrapping porous mass is reduced. It should be understood that, in no case, should the applied pressure exceed the maximum pressure capacity of the vessel.

DESCRIPTION OF THE DRAWING The above and other features of the present invention will beome more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. l is a vertical cross-sectional view through a vessel according to the invention, the parts being shown somewhat diagrammatically; and

FIG. 2 is a sequence diagram illustrating the steps of the present method.

SPECIFIC DESCRIPTION In FIG. I, I show a pressure-retentive vessel 1, having a cylindrical wall portion la closed at the top and bottom by hemispherical portions 1b and 10, respectively, here shown to be unitary within wall I. In practice, these parts may be formed on separate members which are joined together at steps, welds or the like in the wall of the vessel. The upper dome 1b is provided with a neck 1d forming a filling and emptying opening 6. The major part of the volume of the vessel is filled with a porous monolithic mass 3 adapted to absorb a solvent such as acetone. This monolithic mass may be composed of diatomaceous earth or other mineral material, with appropriate binder, capable of forming a highly porous structure. Between the porous mass 3 and the wall la, 1b of the vessel, there is formed a space filled with fine-grained sinter metal particles 2 which are sintered together to form a coherent rigid body. In the region 5 of the gas-collecting space around the porous mass 3, close to the inlet or outlet fitting 1d, the porous mass 3 is provided with a recess 3a designed to increase the thickness of the sintered metal layer in the region of the fitting id. The sintered mass has thus a greater thickness in the region of the opening to increase the effectiveness as a flame barrier.

Referring now to FIG. 2, in which I show a vessel I having an upper hemispheric dome lb which is fastened to the wall Ia at a step ls, it will be seen that the first step (I) is to introduce a slurry of solids and water into the vessel during the porous-core casting operation. The vessel is then heated as symbolized at w to dry the slurry into the porous mass 3' (step II) which shrinks away from the wall of the vessel I to define the space 2a. Before the porous mass has been baked thoroughly, a plunger llll is introduced to shape the recess 3a in the porous body 3.

In the next stage (III), the sinter particles 2' are introduced under pressure. To this end, a high-pressure pump I2 may be connected to the opening 6 and can force particles into the space Zn from a hopper 13. The pressure, measured at I4, preferably lies just below the pressure capacity of the vessel 1' so that, without bursting, the latter may be expanded to a diameter D ii from its original diameter D (compare steps II and III). When the pressure is relieved, the contraction of the walls applies a prestress to the porous body 3' as represented by the arrows I5. In step IV, a ram 4 is introduced through the opening 6 to densify the particle mass at 5', whereupon the assembly is sintered under pressure in step 5. The chamber 16 represents a pressure container in which the vessel may be held from the time in which it is to be filled with the sinter particles through the final sintering stage.

SPECIFIC EXAMPLE An acetylene vessel, having a acpacity of 8.5 m (STP) and an acetylene delivery pressure of i8 kglcm is composed of steel and has a nominal bursting pressure of kg/cm and an empty volume of 50 liters.

The cylindrical vessel has a wall thickness of 3.5 mm, an internal diameter of 26 cm and end caps or domes of the type described in connection with FIG. 1. The vertical height of the vessel is 110 cm.

An aqueous slurry (22 percent by weight solids) of material for porous mass 3 is introduced into the vessel until the latter is filled to a point just below the inlet and outlet fitting. The vessel is slowly heating to a temperature of 105C and held at this temperature to bake and dry the slurry. The resulting porous mass occupies percent of the volume of the vessel leaving a space which increases in cross-section from top to bottom. The porous mass has a capacity of 19.5 liters of acetone a porosity of 90 percent and an average pore width of 0.0001 mm.

Into the space surrounding the porous mass is introduced under gas pressure of 18 kg/cm gauge, 200 g of aluminum-alloy powder having a particle size of 0.4 mm and approximately spheroidal configuration. The aluminum-alloy powder of 5 to 7 percent by weight silicon, 0.1 to 0.3 percent by weight magnesium, 0.3 to 0.6 percent by weight manganese, 3 to 5 percent by weight copper and the balance aluminum. The pressure used to introduce the particles expands the walls of the vessel slightly. The particle mass in the region 5 is then densified by mechanical compaction via the ram 4 at a pressure of 40 kg/cm and the system is thereafter sintered at a temperature of 500 C for a period of 0.5 hours. The porous mass 2, 2' has a porosity of 40 percent, an average pore diameter of 0.1 mm and an average pore length of 0,4 mm.

1 claim:

1. A pressurized-gas tank for an explosive gas, soluble in a solvent, comprising:

a pressure-retentive vessel having an outlet and at least one wall surrounding the space within said vessel",

a porous mass adapted to receive said solvent and said gas in said space in said vessel and spaced with all-around clearance from said wall thereof to form with said wall an annular intervening space communicating with said outlet and surrounding said porous mass; and

a body of fine-grained particles sintered together and filling said annular intervening space whereby the body of sintered particles envelops said porous mass.

2. The pressurized-gas tank defined in claim 1 wherein said body is chemically inert with respect to said gas and said solvent.

3. The pressurized-gas tank defined in claim 1 wherein said body has a melting point below the decomposition temperature of said gas and said solvent.

4. The pressurized-gas tank defined in claim 1 wherein said body is composed of metal particles.

5. A pressurized-gas tank for an explosive gas, soluble in a solvent, comprising:

a pressure-retentive vessel;

a porous mass adapted to receive said solvent and said gas in said vessel and spaced from at least one wall thereof to form with said wall an intervening space; and

a body of fine-grained metal particles sintered together and filling said space, said metal particles having the following composition:

5 to 7 percent by weight silicon 0.1 to 0.3 percent by weight magnesium 0.3 to 0.6 percent by weight manganese, and

3 to 5 percent by weight copper,

balance aluminum.

6. A method of making a pressurized-gas tank, comprising the steps of:

a. pouring an aqueous slurry of a hardenable material into a pressure-retentive vessel;

b. driving off water from said slurry and hardening same to produce a porous solvent-absorptive mass shrinking away from a wall of said vessel to define a space therewith;

c. filling said space with finely divided particles of a sinterable material; and

d. heating said vessel to sinter said particles into a porous body.

7. The method defined in claim 6 wherein said particles are introduced into said space by forcing the particles into said vessel under a pressure differential.

8. The method defined in claim 7 wherein said pressure differential is sufficient to expand said vessel, said method further comprising the step of relaxing the pressure in said vessel to retain said porous mass under compression.

9. The method defined in claim 6, further comprising the step of maintaining the interior of said vessel under pressure during the introduction of said particles into said space and during sintering of said particles together.

10. The method defined in claim 6, further comprising the step of mechanically densifying said particles in said space prior to sintering said particles. 

1. A pressurized-gas tank for an explosive gas, soluble in a solvent, comprising: a pressure-retentive vessel having an outlet and at least one wall surrounding the space within said vessel; a porous mass adapted to receive said solvent and said gas in said space in said vessel and spaced with all-around clearance from said wall thereof to form with said wall an annular intervening space communicating with said outlet and surrounding said porous mass; and a body of fine-grained particles sintered together and filling said annular intervening space whereby the body of sintered particles envelops said porous mass.
 2. The pressurized-gas tank defined in claim 1 wherein said body is chemically inert with respect to said gas and said solvent.
 3. The pressurized-gas tank defined in claim 1 wherein said body has a melting point below the decomposition temperature of said gas and said solvent.
 4. The pressurized-gas tank defined in claim 1 wherein said body is composed of metal particles.
 5. A pressurized-gas tank for an explosive gas, soluble in a solvent, comprising: a pressure-retentive vessel; a porous mass adapted to receive said solvent and said gas in said vessel and spaced from at least one wall thereof to form with said wall an intervening space; and a body of fine-grained metal particles sintered together and filling said space, said metal particles having the following composition: 5 to 7 percent by weight silicon 0.1 to 0.3 percent by weight magnesium 0.3 to 0.6 percent by weight manganese, and 3 to 5 percent by weight copper, balance aluminum.
 6. A method of making a pressurized-gas tank, comprising the steps of: a. pouring an aqueous slurry of a hardenable material into a pressure-retentive vessel; b. driving off water from said slurry and hardening same to produce a porous solvent-absorptive mass shrinking away from a wall of said vessel to define a space therewith; c. filling said space with finely divided particles of a sinterable material; and d. heating said vessel to sinter said particles into a porous body.
 7. The method defined in claim 6 wherein said particles are introduced into said space by forcing the particles into said vessel under a pressure differential.
 8. The method defined in claim 7 wherein said pressure differential is sufficient to expand said vessel, said method further comprising the step of relaxing the pressure in said vessel to retain said porous mass under compression.
 9. The method defined in claim 6, further comprising the step of maintaining the interior of said vessel under pressure during the introduction of said particles into said space and during sintering of said particles together.
 10. The method defined in claim 6, further comprising the step of mechanically densifying said particles in said space prior to sintering said particles. 